Squealing in front driver's side wheel area

I have a 2003 Subaru Forester with 39,500 miles. Automatic transmission, AWD. Today it developed a loud metallic squeal in front driver side wheel area. It’s frequency speeds up when I go faster, and goes away as soon as I step on the brake. It makes the noise both in forward and reverse, but not when the car is sitting still and idling.
I have to drive to Boston on Tuesday which is 395 miles. Any ideas what this could be? Does anybody think it’s a bad idea to drive it on such a long trip if I can’t get it seen by my mechanic on Monday?

Possibly rock of some foreign matter in brake. Where you on gravel or through any mud.
Take a look,maybe you can see it. Ive had this same thing happen and noise goes away when hit the brake.
Long trip safe? Thats questionable. Probably. Ive alway had the (rock?) fall out after awhile.
How far have you driven it since the noise started?

I’d have someone look at the brakes before Tuesday’s trip. It sounds to me like the brake wear indicator which means you’re close to needing new brake pads. Sometimes those things give fairly early warning & you have some time & miles. Sometimes not. I’d have someone take a look on Monday to inspect & if its the brake pads tell you whether you can go to Boston & back.

Thanks so much for the advice! I was able to get the brakes looked at on Saturday and it was the wear indicator making the noise. I was even able to get the front brakes and rotors replaced, so I’m all set for my trip.